HFE (gene) explained

Human homeostatic iron regulator protein, also known as the HFE protein (High FE2+), is a transmembrane protein that in humans is encoded by the HFE gene. The HFE gene is located on short arm of chromosome 6 at location 6p22.2 [1]

Function

The protein encoded by this gene is an integral membrane protein that is similar to MHC class I-type proteins and associates with beta-2 microglobulin (beta2M). It is thought that this protein functions to regulate circulating iron uptake by regulating the interaction of the transferrin receptor with transferrin.[2]

The HFE gene contains 7 exons spanning 12 kb.[3] The full-length transcript represents 6 exons.[4]

HFE protein is composed of 343 amino acids. There are several components, in sequence: a signal peptide (initial part of the protein), an extracellular transferrin receptor-binding region (α1 and α2), a portion that resembles immunoglobulin molecules (α3), a transmembrane region that anchors the protein in the cell membrane, and a short cytoplasmic tail.

HFE expression is subjected to alternative splicing. The predominant HFE full-length transcript has ~4.2 kb. Alternative HFE splicing variants may serve as iron regulatory mechanisms in specific cells or tissues.[5]

HFE is prominent in small intestinal absorptive cells,[6] [7] gastric epithelial cells, tissue macrophages, and blood monocytes and granulocytes,[8] and the syncytiotrophoblast, an iron transport tissue in the placenta.[9]

Clinical significance

The iron storage disorder hereditary hemochromatosis (HHC) is an autosomal recessive genetic disorder that usually results from defects in this gene.

The disease-causing genetic variant most commonly associated with hemochromatosis is p. C282Y.[10] About 1/200 of people of Northern European origin have two copies of this variant; they, particularly males, are at high risk of developing hemochromatosis.[11] This variant may also be one of the factors modifying Wilson's disease phenotype, making the symptoms of the disease appear earlier.[12]

Allele frequencies of HFE C282Y in ethnically diverse western European white populations are 5-14%[13] [14] and in North American non-Hispanic whites are 6-7%.[15] C282Y exists as a polymorphism only in Western European white and derivative populations, although C282Y may have arisen independently in non-whites outside Europe.[16]

HFE H63D is cosmopolitan but occurs with greatest frequency in individuals of European descent.[17] [18] Allele frequencies of H63D in ethnically diverse western European populations are 10-29%.[19] and in North American non-Hispanic whites are 14-15%.[20]

At least 42 mutations involving HFE introns and exons have been discovered, most of them in persons with hemochromatosis or their family members.[21] Most of these mutations are rare. Many of the mutations cause or probably cause hemochromatosis phenotypes, often in compound heterozygosity with HFE C282Y. Other mutations are either synonymous or their effect on iron phenotypes, if any, has not been demonstrated.

Interactions

The HFE protein interacts with the transferrin receptor TFRC.[22] [23] Its primary mode of action is the regulation of the iron storage hormone hepcidin.[24]

Hfe knockout mice

It is possible to delete part or all of a gene of interest in mice (or other experimental animals) as a means of studying function of the gene and its protein. Such mice are called “knockouts” with respect to the deleted gene. Hfe is the mouse equivalent of the human hemochromatosis gene HFE. The protein encoded by HFE is Hfe. Mice homozygous (two abnormal gene copies) for a targeted knockout of all six transcribed Hfe exons are designated Hfe−/−.[25] Iron-related traits of Hfe−/− mice, including increased iron absorption and hepatic iron loading, are inherited in an autosomal recessive pattern. Thus, the Hfe−/− mouse model simulates important genetic and physiological abnormalities of HFE hemochromatosis. Other knockout mice were created to delete the second and third HFE exons (corresponding to α1 and α2 domains of Hfe). Mice homozygous for this deletion also had increased duodenal iron absorption, elevated plasma iron and transferrin saturation levels, and iron overload, mainly in hepatocytes.[26] Mice have also been created that are homozygous for a missense mutation in Hfe (C282Y). These mice correspond to humans with hemochromatosis who are homozygous for HFE C282Y. These mice develop iron loading that is less severe than that of Hfe−/− mice.[27]

HFE mutations and iron overload in other animals

The black rhinoceros (Diceros bicornis) can develop iron overload. To determine whether the HFE gene of black rhinoceroses has undergone mutation as an adaptive mechanism to improve iron absorption from iron-poor diets, Beutler et al. sequenced the entire HFE coding region of four species of rhinoceros (two browsing and two grazing species). Although HFE was well conserved across the species, numerous nucleotide differences were found between rhinoceros and human or mouse, some of which changed deduced amino acids. Only one allele, p.S88T in the black rhinoceros, was a candidate that might adversely affect HFE function. p.S88T occurs in a highly conserved region involved in the interaction of HFE and TfR1.[28]

See also

Further reading

Notes and References

  1. Web site: HGNC: HFE. 2019-08-30 .
  2. Web site: NCBI Gene: HFE homeostatic iron regulator. 30 November 2020 . National Center for Biotechnology Information.
  3. Feder. JN. Gnirke. A. Thomas. W. Tsuchihashi. Z. Ruddy. DA. Basava. A. Dormishian. F. Domingo R. Jr. Ellis. MC. Fullan. A. Hinton. LM. Jones. NL. Kimmel. BE. Kronmal. GS. Lauer. P. Lee. VK. Loeb. DB. Mapa. FA. McClelland. E. Meyer. NC. Mintier. GA. Moeller. N. Moore. T. Morikang. E. Prass. CE. Quintana. L. Starnes. SM. Schatzman. RC. Brunke. KJ. Drayna. DT. Risch. NJ. Bacon. BR. Wolff. RK. A novel MHC class I-like gene is mutated in patients with hereditary haemochromatosis. Nature Genetics. August 1996. 13. 4. 399–408. 8696333. 10.1038/ng0896-399. 26239768.
  4. Web site: Dorak. M.T.. March 2008. HFE (hemochromatosis). 17 June 2020. Atlas of Genetics and Cytogenetics in Oncology and Haematology. 29 September 2017. https://web.archive.org/web/20170929113814/http://atlasgeneticsoncology.org/Genes/GC_HFE.html. dead.
  5. Martins. R. Silva. B. Proença. D. Faustino. P. Differential HFE gene expression is regulated by alternative splicing in human tissues. PLOS ONE. 3 March 2011. 6. 3. e17542. 21407826. 10.1371/journal.pone.0017542. 3048171. 2011PLoSO...617542M. free.
  6. Waheed. A. Parkkila. S. Saarnio. J. Fleming. RE. Zhou. XY. Tomatsu. S. Britton. RS. Bacon. BR. Sly. WS. Association of HFE protein with transferrin receptor in crypt enterocytes of human duodenum. Proceedings of the National Academy of Sciences of the United States of America. 16 February 1999. 96. 4. 1579–84. 9990067. 10.1073/pnas.96.4.1579. 15523. 1999PNAS...96.1579W. free.
  7. Griffiths. WJ. Kelly. AL. Smith. SJ. Cox. TM. Localization of iron transport and regulatory proteins in human cells. QJM: Monthly Journal of the Association of Physicians. September 2000. 93. 9. 575–87. 10984552. 10.1093/qjmed/93.9.575.
  8. Parkkila. S. Parkkila. AK. Waheed. A. Britton. RS. Zhou. XY. Fleming. RE. Tomatsu. S. Bacon. BR. Sly. WS. Cell surface expression of HFE protein in epithelial cells, macrophages, and monocytes. Haematologica. April 2000. 85. 4. 340–5. 10756356.
  9. Parkkila. S. Waheed. A. Britton. RS. Bacon. BR. Zhou. XY. Tomatsu. S. Fleming. RE. Sly. WS. Association of the transferrin receptor in human placenta with HFE, the protein defective in hereditary hemochromatosis. Proceedings of the National Academy of Sciences of the United States of America. 25 November 1997. 94. 24. 13198–202. 9371823. 10.1073/pnas.94.24.13198. 24286. 1997PNAS...9413198P. free.
  10. Hsu CC, Senussi NH, Fertrin KY, Kowdley KV . Iron overload disorders . Hepatol Commun. June 2022 . 6 . 8 . 1842–1854 . 35699322 . 10.1002/hep4.2012. 9315134 .
  11. Web site: Hemochromatosis . 20 August 2009 . https://web.archive.org/web/20070318063028/http://digestive.niddk.nih.gov/ddiseases/pubs/hemochromatosis/index.htm . 18 March 2007 . dead .
  12. Gromadzka G, Wierzbicka DW, Przybyłkowski A, Litwin T . Effect of homeostatic iron regulator protein gene mutation on Wilson's disease clinical manifestation: original data and literature review . The International Journal of Neuroscience . 894–900 . November 2020 . 132 . 9 . 33175593 . 10.1080/00207454.2020.1849190. 226310435 .
  13. Book: Porto. Graca. de Sousa. Maria. Barton. James C.. Edwards. Corwin Q.. Variation of hemochromatosis prevalence and genotype in national groups. 2000. Cambridge University Press. In: Hemochromatosis: Genetics, pathophysiology, diagnosis and treatment. 978-0521593809. 51–62.
  14. Ryan. E. O'Keane. C. Crowe. J. Hemochromatosis in Ireland and HFE. Blood Cells, Molecules & Diseases. December 1998. 24. 4. 428–32. 9851896. 10.1006/bcmd.1998.0211.
  15. Acton. RT. Barton. JC. Snively. BM. McLaren. CE. Adams. PC. Harris. EL. Speechley. MR. McLaren. GD. Dawkins. FW. Leiendecker-Foster. C. Holup. JL. Balasubramanyam. A. Hemochromatosis and Iron Overload Screening Study Research Investigators. Geographic and racial/ethnic differences in HFE mutation frequencies in the Hemochromatosis and Iron Overload Screening (HEIRS) Study. Ethnicity & Disease. 2006. 16. 4. 815–21. 17061732.
  16. Rochette. J. Pointon. JJ. Fisher. CA. Perera. G. Arambepola. M. Arichchi. DS. De Silva. S. Vandwalle. JL. Monti. JP. Old. JM. Merryweather-Clarke. AT. Weatherall. DJ. Robson. KJ. Multicentric origin of hemochromatosis gene (HFE) mutations. American Journal of Human Genetics. April 1999. 64. 4. 1056–62. 10090890. 10.1086/302318. 1377829.
  17. Merryweather-Clarke. AT. Pointon. JJ. Shearman. JD. Robson. KJ. Global prevalence of putative haemochromatosis mutations. Journal of Medical Genetics. April 1997. 34. 4. 275–8. 9138148. 10.1136/jmg.34.4.275. 1050911.
  18. Merryweather-Clarke. AT. Pointon. JJ. Jouanolle. AM. Rochette. J. Robson. KJ. Geography of HFE C282Y and H63D mutations. Genetic Testing. 2000. 4. 2. 183–98. 10953959. 10.1089/10906570050114902.
  19. Book: Fairbanks. Virgil F.. Barton. James C.. Edwards. Corwin Q.. Hemochromatosis: population genetics. In: Hemochromatosis: Genetics, pathophysiology, diagnosis and treatment. 2000. Cambridge University Press. 978-0521593809. 42–50.
  20. Acton. RT. Barton. JC. Snively. BM. McLaren. CE. Adams. PC. Harris. EL. Speechley. MR. McLaren. GD. Dawkins. FW. Leiendecker-Foster. C. Holup. JL. Balasubramanyam. A. Hemochromatosis and Iron Overload Screening Study Research Investigators. Geographic and racial/ethnic differences in HFE mutation frequencies in the Hemochromatosis and Iron Overload Screening (HEIRS) Study. Ethnicity & Disease. 2000. 16. 4. 815–21. 17061732.
  21. Book: Edwards. Corwin Q.. Barton. James C.. Greer. John P.. Arber. Daniel A.. Glader. Bertil. List. Alan F.. Means. Robert T. Jr.. Paraskevas. Frixos. Rodgers. George M.. Hemochromatosis. In: Wintrobe's Clinical Hematology. 2014. Wolters Kluwer/Lippincott Williams & Wilkins. 9781451172683. 662–681.
  22. Feder JN, Penny DM, Irrinki A, Lee VK, Lebrón JA, Watson N, Tsuchihashi Z, Sigal E, Bjorkman PJ, Schatzman RC . The hemochromatosis gene product complexes with the transferrin receptor and lowers its affinity for ligand binding . Proceedings of the National Academy of Sciences of the United States of America . 95 . 4 . 1472–7 . February 1998 . 9465039 . 19050 . 10.1073/pnas.95.4.1472 . 1998PNAS...95.1472F . free .
  23. West AP, Bennett MJ, Sellers VM, Andrews NC, Enns CA, Bjorkman PJ . Comparison of the interactions of transferrin receptor and transferrin receptor 2 with transferrin and the hereditary hemochromatosis protein HFE . The Journal of Biological Chemistry . 275 . 49 . 38135–8 . December 2000 . 11027676 . 10.1074/jbc.C000664200 . free .
  24. Nemeth E, Ganz T . Regulation of iron metabolism by hepcidin . Annual Review of Nutrition . 26 . 323–342 . 2006 . 16848710 . 10.1146/annurev.nutr.26.061505.111303 .
  25. Zhou. XY. Tomatsu. S. Fleming. RE. Parkkila. S. Waheed. A. Jiang. J. Fei. Y. Brunt. EM. Ruddy. DA. Prass. CE. Schatzman. RC. O'Neill. R. Britton. RS. Bacon. BR. Sly. WS. HFE gene knockout produces mouse model of hereditary hemochromatosis. Proceedings of the National Academy of Sciences of the United States of America. 3 March 1998. 95. 5. 2492–7. 9482913. 10.1073/pnas.95.5.2492. 19387. 1998PNAS...95.2492Z. free.
  26. Bahram. S. Gilfillan. S. Kühn. LC. Moret. R. Schulze. JB. Lebeau. A. Schümann. K. Experimental hemochromatosis due to MHC class I HFE deficiency: immune status and iron metabolism. Proceedings of the National Academy of Sciences of the United States of America. 9 November 1999. 96. 23. 13312–7. 10557317. 10.1073/pnas.96.23.13312. 23944. 1999PNAS...9613312B. free.
  27. Levy. JE. Montross. LK. Cohen. DE. Fleming. MD. Andrews. NC. The C282Y mutation causing hereditary hemochromatosis does not produce a null allele. Blood. 1 July 1999. 94. 1. 9–11. 10381492. 10.1182/blood.V94.1.9.413a43_9_11. 12722648 .
  28. Beutler. E. West. C. Speir. JA. Wilson. IA. Worley. M. The hHFE gene of browsing and grazing rhinoceroses: a possible site of adaptation to a low-iron diet. Blood Cells, Molecules & Diseases. 2001. 27. 1. 342–50. 11358396. 10.1006/bcmd.2001.0386.

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